c251_15 - Faradays Law: Faradays Law: Electromagnetic...

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1 •In the early 1830s Michael Faraday made the observation that a changing current I P in one electric circuit can cause current to appear (“ induce a current I S ”) in a second circuit. B I S I P Primary Circuit: Source Secondary Circuit: Faraday’s Law: Electromagnetic Induction 2 Faraday’s Law : “The electromotive force, V emf , induced around a closed loop L is equal to the time rate of decrease of the magnetic flux linking the loop.” loop the through flux the is ψ = = where dt d V emf ψ For a coil of N tightly wound turns ∫∫ = = S emf S d . B dt d N V r r where d S S ∫∫ = S d . dt B d V emf r r B 3 Example ρ I=I 0 cos( ω t) N small coils ) t sin( 2 I NA dt d V o o coil emf πρ μ = = coil o o o A ) t , ( B ) t cos( 2 I 2 I ) t , ( B = = V emf t Ψ t 4 Faraday’s Law : Faraday’s law applies to situations where 1) the B-field is a function of time, i.e., B=B o cos ω t, loop is fixed 2) d S is a function of time, B is static and the loop is moving 3) B and d S are functions of time. d S B = L emf L d . E V , E r r . E V L emf r r r r d L E Case 1: I(t) B(t)
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This note was uploaded on 07/11/2011 for the course ELEC 251 taught by Professor Lynch during the Spring '10 term at Concordia Canada.

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c251_15 - Faradays Law: Faradays Law: Electromagnetic...

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